Roast eggplants: Using a wooden skewer, pierce eggplants all over. Turn two gas burners or a gas grill to high flame; place one eggplant on each. Cook, turning with tongs as each side blackens and softens, until skins are completely black and flesh is falling-apart tender, about 10 minutes. Remove from flame; transfer to a nonreactive baking dish. Place one end of dish on a slant so that the juices can run from the eggplants. When cool enough to handle, peel away all blackened skin.
Place eggplant flesh in the bowl of a food processor; pulse until pureed. Transfer to a large bowl; stir in the onion, tomatoes, parsley, olive oil, lemon juice, salt, and pepper. Serve warm or at room temperature with pita or rye bread.
Instead of cooking the eggplant over an open flame, you can use the oven: Place the eggplant in a shallow baking pan under the broiler. Broil, turning the eggplant every five minutes until skin is blackened all over and the flesh is falling-apart tender, twenty to thirty minutes.